PROJECT SUMMARY/ABSTRACT In 2016, US Preventative Services Task Force (USPSTF) concluded that there is insufficient evidence (grade ?I?) to support universal screening for autism spectrum disorder (ASD) in primary care. They end their report with multiple suggestions for future research, including: 1) studies that assess the impact of false positive screening on families, and 2) studies that explore characteristics of children, families, and systems that are more and less effectively engaged in the screening, diagnosis, and treatment process. To move the Task Force from an ?I? recommendation, studies are needed that respond to the USPSTF suggestions for future research. Our current R01, which is already prospectively collecting data on a large sample of children who screen positives for ASD in primary care for 12-months, creates an opportunity ? with only a small amount of additional data collection ? to address many of the Task Force?s suggestions for future work. First, we will use these data to identify children with a false-positive ASD screen (estimate n=130) and measure benefits (e.g. frequency of alternate diagnoses, access to services) and harms (e.g. parental distress) in these families by: 1) Performing a structured chart review to identify/confirm false-positive screens; 2) Using regression and proportional hazards modeling to compare parent-reported measures (e.g., stress, social support), and systems measures (time to diagnosis) between families with false-positive and true-positive ASD screen; and 3) conducting semi-structured interviews with a subset of false-positive families to further explore experiences. Then, using Kaplan-Meier plots, Cox proportional hazards modeling, and multivariable logistic regression analyses, we will assess the impact of parent concern (reported at the time of an ASD screen) on how families progress through each stage of the diagnosis and treatment framework as proposed by the USPSFT, as well as impact on parent-reported outcomes. The goal of these investigations is to provide data needed to move the Task Force from an ?I? to a formal recommendation.